Frequency converter



FIG. 1 is a perspective view of a frequency converter showing our new design;

FIG. 2 is a front view thereof,

FIG. 3 is a rear view thereof,

FIG. 4 is a left side view thereof,

FIG. 5 is a right side view thereof,

FIG. 6 is a top view thereof,

FIG. 7 is a bottom view thereof,

FIG. 8 is a second perspective view thereof,

FIG. 9 is a third perspective view thereof; and,

FIG. 10 is a fourth perspective view thereof.

The broken lines shown in FIGS. 1-10 represent unclaimed subject matter and form no part of the claimed design. 

CLAIM The ornamental design for a frequency converter, as shown and described. 